The objective of this study was to assess the association between alcohol drinking before and during pregnancy and the risk of spontaneous abortion using data from a case-control study conducted in Milan, Italy. A total of 462 women (median age 30 years) were admitted for spontaneous abortion (within the 12th week of gestation) to a network of obstetrics departments in the greater Milan area. Of these, 148 (32%) were between the fourth and the eighth week of gestation and 314 (68%) between the ninth and the 12th week. A control group was made up of 814 women (median age 29 years) who gave birth at term (> 37 weeks gestation) to healthy infants (Apgar 5th minute > or = 8, weight > or = 3000 g) on randomly selected days at the same hospitals where cases had been identified. A total of 212 cases (46%) and 355 controls (47%) reported alcohol drinking before conception. Considering non-drinkers as the reference category, the relative risks (RR) of spontaneous abortion were 1.2 [95% confidence interval (CI), 0.9-1.6] and 0.8 (95% CI, 0.6-1.1), respectively, in drinkers of one to seven and more than seven drinks per week before conception. No association emerged between the duration of alcohol drinking and the risk of spontaneous abortion. A total of 166 cases (35.9%) and 263 (32.3%) controls reported any alcohol drinking during the first trimester of pregnancy. The corresponding relative risk was 1.1 (95% CI, 0.9-1.4) and no relationship emerged between the number of drinks per week and the risk of abortion.(ABSTRACT TRUNCATED AT 250 WORDS)